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MA: Fachverband Magnetismus

MA 31: Magnetization and Demagnetization Dynamics II

MA 31.4: Talk

Wednesday, March 9, 2016, 10:15–10:30, H34

The role of non-equilibrium hot electrons in ultrafast laser-induced demagnetization — •Ilya Razdolski¹, Alexandr Alekhin¹, Ulrike Martens², Markus Münzenberg², and Alexey Melnikov¹ — ¹Fritz-Haber-Institut der MPG, Berlin, Germany — ²Ernst-Moritz-Arndt Universität, Institut für Physik, Greifswald, Germany

Ultrafast demagnetization of thin transition metal films in the absence of the hot carrier transport is studied by time-resolved magneto-optical Kerr effect (MOKE) with 20 fs resolution for various laser fluences. We demonstrate that the key role in the ultrafast magnetization dynamics is played by the non-equilibrium hot electrons, in line with previous theoretical studies. The demagnetization timescale of about 200 fs is determined by their thermalization due to the electron-electron interaction. The subsequent re-magnetization occurs on 1 ps timescale of the electron-lattice interaction. Further, we suggest an approach for the MOKE experiments which allows for the disentanglement of the magnetization dynamics and optical effects by measuring a complete set of the transient optical response data, including reflectivity, MOKE rotation, and ellipticity.